Stratigraphy of deep-water Cretaceous deposits in Gyangze, southern Tibet, China

Extensive tectonic activity in southern Tibet (Tibetan Tethys Himalayas) resulted in overthrusting and tectonic deformation of Cretaceous strata, which in the study area was not recognized by earlier researchers. Field studies of three typical cross-sections in southern Tibet has led to the revision of previous stratigraphy. The thickness of the Cretaceous in Gyangze varies between 300 and 700 m, but is not over 2000 m as previously estimated at Gyabure and Weimei, where the strata are overturned and repeated owing to previously unrecognized thrusts. In upward stratigraphic order four lithological markers were used in the field study: belemnite and black marker, lenticular limestone and white marker, red marker, and olistolith marker. The first two of these are associated with the fine-grained clastic shelf sequence of the Gyabula Formation, which is of Berriasian-early Santonian age. The third is the deep-sea red-beds marker of the Chuangde Formation, dated as middle Santonian-early Campanian. The fourth depicts the slump facies and olistolith of the middle Campanian-Paleocene Zongzhuo Formation. The revised Cretaceous stratigraphy provides a framework for studies of the pelagic red beds of the Chuangde Formation, which is intermittently exposed in southern Tibet.